Sustainable closed-loop recycling of spent graphite anodes via pre-oxidation and carbon coating

Abstract

To achieve high-value recovery of graphite anodes from spent lithium-ion batteries, conventional hydrometallurgical and pyrometallurgical routes face environmental and economic bottlenecks, including complex wastewater treatment, high energy consumption and equipment corrosion. This study proposes a regeneration strategy involving pre-oxidation at 550 °C, ball-milling with polyvinyl alcohol (PVA) and subsequent calcination at 900 °C. During this process, the reducing gases generated from PVA pyrolysis remove oxygen-containing functional groups, while the carbonization of PVA simultaneously forms an amorphous carbon coating. This process eliminates the need for strong acid/alkali leaching or corrosive molten salts, thus avoiding toxic wastewater and hazardous gas emissions wwhile significantly reducing energy consumption and carbon footprint. During regeneration, reducing gases generated from PVA pyrolysis in situ remove oxygen-containing functional groups introduced by pre-oxidation, while the amorphous carbon coating effectively repairs surface defects. The optimized sample (RG@10%) assembled with LiFePO 4 in a full cell delivers a reversible capacity of 136.8 mA h g −1 after 200 cycles. Economic assessment indicates a profit of 2.575 $ kg −1 , and both energy consumption and CO 2 emissions are lower than those of conventional methods. This strategy combines simplicity, energy efficiency, low carbon emissions, zero secondary pollution and economic feasibility, offering a practical green route for sustainable closed-loop recycling of spent graphite anodes.